Treatment of cellulose products



United States Patent 3,118,725 TREATMENT OF CELLULGSE PRODUCTS Charles L. Henry, Bernmd J. Barrett, and Clyde M. Guest,

In, Candler, and Nicholas Flores, Erika, N.C., assiguors to American Enka Corporation, Enka, N.C., a corporation of Delaware No Drawing. Filed Aug. 8, 1960, Ser. No. 47,959 4 Claims. (Cl. 8-116.4)

This invention relates to a new process for the chemical modification of cellulose products whereby said products have improved properties and characteristics. More specifically, this invention is a process for the treatment of rayon fibers and filamentary yarns with a polymeric acetal derived from ethylene glycol and formaldehyde together with monomeric formaldehyde under a specific set of conditions as regards concentrations, catalysts, buffer, pH, and drying and curing temperatures.

Conventional rayon fibers and yarns produce fabrics which have several properties and characteristics which mitigate against them in certain end-uses. That is, alkali resistance is not adequate for textile processes such as mercerization; water imbibition is high as shown by a high swelling value; fabric hand is not full and resilient; and, dimensional shrinkage occurs upon repeated washings.

The object of this invention is to provide a process for improving these properties by chemically modifying the cellulose fibers or yarns.

Another object is to provide a process whereby this chemical modification is obtained economically and permanently without substantial losses in tensile strengths or abrasion resistance and without use of nitrogen-containing agents which could cause retention of chlorine during bleaching.

The art of chemically modifying cellulose textile materials by the application of resins, cross-linking agents and the like is Well known and extensive. However, no existing process is ideal and further improvements are needed. Many existing processes cause high losses in tensile strength and abrasion resistance; many cause fabric discoloration; many are not economically feasible; most employ nitrogen-containing agents which cause tendering and odors via chlorine retention during chlorine bleachings; and most are not adequately stable to repeated launderings.

A major portion of the art of chemically modifying cellulose textile products relates to the use of formaldehyde or products which possess functional groups derived from formaldehyde. Formaldehyde alone has limited use for the chemical modification of rayon fibers or filaments, as the fibers or filaments are embrittled to the extent that their processability into fabrics and their utility are impaired so that they are commercially unacceptable. However, it has now been found that formaldehyde can be successfully employed to modify rayon fibers or filaments without substantial embrittlement by using it in conjunction with a polymeric acetal of the type described in United States Patents 2,785,949 and 2,786,081, provided the treatment is carried out under the specific conditions hereinafter described. The use of the mixture is preferred over the use of the polymeric acetal alone, as the mixture offers an economic advantage and also, for comparable concentrations, produces the desired effects to a greater extent on the fibers or filaments and consequently on the fabrics produced therefrom.

In general terms, the objects of this invention are accomplished by applying to the cellulose fibers or filamentary yarns an aqueous solution of pH 5.0-7.5 containing (1) a polymeric acetal derived from ethylene glycol and formaldehyde of the following formula:

ICC

where n l and X and Y are either H or CH OH, (2) monomeric formaldehpde, (3) an organic acid with at least one carboxylic acid group with an ionization constant lying between 1 l0- and l l0' and (4) magnesium chloride. Then, after excess liquid is pressed out from the cellulose mass to give the desired percentage pick-up, it is dried and a reaction between the cellulose, formaldehyde and polymeric acetal is effected by uniformly heating at an elevated temperature.

Concentrations of the components in the treating bath may be varied according to the magnitude of the effects desired on the fiber or filament properties. The following ranges are preferred for a pick-up of about to 200%. All percentages are based on the weight of the bath.

(1) Ethylene glycol-formaldehyde polymeric acetal:

0.25% to about 5.0%

(2) Formaldehyde: 0.25% to about 5.0%

(3) Organic acid: 0.05% to about 0.5%

(4) Magnesium chloride: 0.20% to about 2.0%

The ratio of monomeric formaldehyde to polymeric acetal in the treating solution is determined by the magnitude of the fiber or filament modification desired; the higher the ratio the greater the effect. The organic acid (as its metal salt) serves the function of bulfering the solution at any selected pH between 5.0 and 7.5. This pH range is preferred as cellulose degradation is controlled during the drying and curing operations. The magnesium chloride serves as a catalyst during the curing operation to effect a reaction between the cellulose, formaldehyde, and polymeric acetal.

After the fibers or filamentary yarns have been treated with the above solution and excess liquid pressed out, the cellulosic mass is dried by heating uniformly at about 70 C. to C. Afterwards the mass is then cured by heating uniformly at C. to C. for 5 to 30 minutes. The correct combination of time and temperature is easily determined by experiment; higher temperatures require shorter times.

For the chemical modification of rayon fibers, it is advantageous to mix the above described treating solution 7 with a lubricating finish so that after the curing operation the fibers are immediately ready for processing into fabric. It has been found that a nonionic polyoxyethylcne sorbitol tallow finish sold under the trade name of Atlas 6-3284 is suitable for this purpose.

A suitable method for preparing the polymeric acetal used in the invention consists of mixing the following components in an apparatus equipped with a reflux condenser and a water trap.

Ethylene glycol, purified grade Paraformaldehyde, USP

6,200 gms. (100 moles). 3,000 gms. (100 moles).

Benzene 1,000 ml. Concentrated sulfuric acid The mixture is refluxed with efiicient stirring for about 10-15 hours until 100 moles of water are removed by azeot-ropic distillation. After cooling, the reaction mixture is neutralized with 20% sodium hydroxide solution. The benzene is then removed by evaporation in vacuo at about 80 C. The product is primarily the desired polymeric acetal and contains about 1% to 3% unreacted formaldehyde.

The following examples are illustrations of this invention.

EXAMPLE 1 Samples of 1100 denier, gel-state viscose rayon yarn containing 720 filaments, were immersed for one hour in solutions containing 2.0% formaldehyde, 0.1% maleic acid (sodium salt), 0.4% magnesium chloride, and varying amounts of the polymeric acctal derived from cthylene glycol and formaldehyde. The pH of the solution was 7. After excess liquid was pressed out to give a pickup of about 125%, the samples were dried at 90 C. and then cured at 140 C. for 20 minutes in a forced draft oven. The resulting data are shown in Table l.

These data show the tempering effect of the polymeric acetal on the action of the formaldehyde. Samples 14 were insoluble in cupriethylenediam-ine showing they were cross-linked by the treatment.

Samples land were soaked for ten minutes at constant length in 7% sodium hydroxide at room temperature. The samples were then washed in running water, acidified with dilute acetic acid, washed acid free, and dried. Cross-linked sample 2 had a residual Wet strength of 94%, while control sample 5 had a residual wet strength. of 80%. These data show the improved alkali resistance of cellulose filaments treated according to this invention.

EXAMPLE II Samples of a 1100 denier, gel-state (not previously dried) viscose rayon yarn containing 720 filaments were treated with a solution containing 0.1% maleic acid (sodium salt), 0.6% magnesium chloride, and varying quantities of polymeric acetal and formal ehyde. The treatment procedure was similar to that of Example I except curing time was minutes. The results are shown in Table II.

' T able 7 II Absolute Break- Breaking Breaking Elong, Polymeric (EH20, Strengths, gins. Percent Swellin g, Acetol, Percent Percent Percent Condi- Wet Condi- Wet tioned tioncd 0 4, 400 800 14.5 15. 5 87 0- 4, 300 .2, 950 14. 5 16.0 88 0 4, 350 2, 800 14. 0 l5. 5 89 0 4-, 450 2, 9-1- 14. 0 14. 5 S6 0. 5 4, 350 2, 900 14. 0 14.- 5 90 1.0 4, 300 3, 000 14. 0 15. 5 80' 2. 0 4, 300 3. 050 g 13. 5 13. 5 60 3. 0 4, 350 3,100 13. 0 13. 5 52 V 4.0 4,300 3,000 12.0 11.5 50 Control 4, 300 3, 000 14. 5 16. 5 98 'Ihe advantage of using the mixture of polymeric acetal and formaldehyde is especially shown by the effects on the swelling values. Fiuther, only the samples tested with the mixture were insoluble in cupriethylenediamine.

, EXAMPLE III 11. Results are given in table 111.

Table III Absolute Breaking Breaking Elongations, Strength, gins. percent Solubility in MgClg, Swelling, in Oupripercent percent ethylenedia Con Conmine di Wet di- Wet tioned tioned 0.1 4,550 2,850 14.5 16. 5 92 Soluble. 0.2 4,450 2, 900 14. 0 14.5 74 D0. 0.4 4,450 3, 050 14.0 14.0 63 Partly soluble. 0.6 4, 450 2, 050 13. 5 14. 5 65 Indoluble.

. 1 3,100 14.0 14.0 64 D0. 3, 000 14. 5 16. 5 9S Soluble.

EXAMPLE IV More samples of the yarn used in Example II were treated with a solution containing 1.0% polymeric acetal, 2.5% formaldehyde, and 0.1% maleic acid of varying pH values. The results in Table IV show that higher elongations and ten-acities are obtained with a solution pH of 5.0 or greater.

Table IV Absolute Breaking Breaking Elonga- Strength gins. tions percent Solution, pH

Condi- Wet Condi- Wet tioned tioued EXAMPLE V Three-pound batches of gel-state, 1.5 denier, 1% inch long viscose rayon staple fiber were soaked for 60 minutes in a bath containing 2.5% formaldehyde, 1.0% polymeric acetal, 0.1% rnaleic acid (sodium salt), and 0.6% magnesium chloride. Solution pH was 7.0. Excess liquid was pressed out giving a pick-up of about The batches were dried at 90-i00 C., passed through a staple fiber heater to open-up the fiber mat, and cured at C. for 25 minutes in a forced draft oven. Fiber swelling was reduced from 61% to 49%, and the fibers were insoluble in cupriethylene-di-amine. The fibers were then water washed, finish applied, dried, and processed into 30/1 spun yarn. Properties of the spun yarn so prepared are compared in Table V with properties of spun yarn prepared from untreated control fibers.

Skeiu Breakfactor A 76 x 74 plain weave fabric Woven from the treated fiber had a significantly more resilient and fuller hand than did a control fabric. Fabric strengths and abrasion resistance for both fabrics were on a very high level as shown in Table VI.

A continuous blanket of freshly spun, washed but with no previous drying, viscose staple fiber was treated on a moving conveyor belt for about one minute with a spray solution consisting of 1.0% formaldehyde, 0.75% polymeric acetal, 0.5% magnesium chloride, 0.1% maleic acid (sodium salt), and 0.5 polyoxyethylene sorbitol tallow finish. Solution pH was 6 to 7, fiber denier was 1.3, and fiber length was 1% inches. Excess liquid was squeezed out to give a pick-up of about 140%. The fiber blanket was broken up and the loose fibers carried on a conveyor belt through a forced draft oven where drying occurred at about 95 0, followed by curing at 132 C. Time of cure was 15 minutes. Upon restoring the fiber moisture content to 11 to 12%, the fibers were ready for processing into spun yarns, as they already had a lubricating finish. Single fiber properties obtained are compared with a control fiber in Table VII.

Table VII Single Fiber Property Treated Control Fiber Fiber nd. Strength, g./d 4.3 4. 3 -W'et Strength, g /d 2. 8 2.8 Cond. Elong, pereent 9.8 11. 6 Wet Elong, percent..." 12. 15 Swelling, percent 62 95 The treated fibers were converted into 30/ 1 yarn and then into a 76 x 74 plain weave fabric. The boiled oif fabric had a more resilient, fuller hand than did a control fabric. Fabric properties listed in Table Vlil show that the chemical modification did not significantly decrease fabric strengths and abrasion resistance, but did substantially improve dimensional stability.

Table VIII Fabric Fabric Fabric Property from from Treated C ontrol Fiber Fiber Grab Strength Test:

Cond. Warp Strength, lbs 59. 5 55 00nd. Filling Strength, is... 56.0 54 Wet Warp Strength, lbs 42.0 43 Wet Filling Strength, lbs 40. 5 42 Stall-Flex Abrasion Test (cycles):

Cond. Warp 540 425 Cond. Fillin"- 460 390 Vv'et Warp. 345 405 Wet Filliug 320 340 Shrinkage After 50 Home Type Launderings (160 F.) and Tumble Drying:

Warp, percent 14.0 17 5 Filling, percent 2.0 8 5 As stated in the first part of the specification, and disclosed in Example VI, the chemical modification of the fibers may be combined with a finishing treatment. This has a great economical advantage in that it eliminates the normal steps of washing and drying the fibers, applying a finish emulsion, and redrying.

Various changes may be made in the embodiments and examples and preferred methods for carrying out our in vention described above, and it will be understood that various changes and modifications may also be made in the materials and procedures within the spirit of our invention and the scope of the appended claims.

W hat claimed is:

1. A process of chemically modifying rayon fibers which comprises applying to the fibers an aqueous solution having a pH between 5.0 and 7.5 and containing by weight of the solution 0.25% to about 5.0% ethylene glycol-formaldehyde polymeric acetal, 0.25% to about 5.0% monomeric formaldehyde, 0.05% to about 0.5% of an alkali metal salt of an organic acid, and 0.2% to about 2.0% of a catalyst, removing the excess liquid whereby a pickup of between and 200% is efiected, drying the fiber at between about 70 C. and C., and thereafter curing the same by uniformly heating at between C. and C. for from 5 to 30 minutes.

2. A process of chemically modifying rayon fibers which comprises applying to the fibers an aqueous solution having a pl-I between 5.0 and 7.5 and containing by weight of the solution 0.25% to about 5.0% ethylene glycolformaldehyde polymeric acetal, 0.25% to about 5.0% monomeric formaldehyde, 0.05% to about 0.5% of an alkali metal salt of an organic acid, and 0.2% to about 2.0% of magnesium chloride, removing the excess liquid, drying the fibers at between about 70 C. and about 110 C., and finally curing the same by uniformly heating at etween 120 C. and 160 C. for 5 to 30 minutes.

3. A process of chemically modifying rayon fibers which comprises applying to the fibers an aqueous solution having a pH between 5.0 and 7.5 and containing by weight of the solution 0.25% to about 5.0% ethylene glycol-formaldehyde polymeric acetal, 0.25% to about 5.0% monomeric formaldehyde, 0.05% to about 0.5% of an alkali metal salt of an organic acid, a nonionic polyoxyethylene sorbitol tallow finish, and 0.2% to about 2.0% of magnesium chloride, removing the excess liquid, drying the fibers at between about 70 C. to about 110 C., and finally curing the same by uniformly heating at between 120 C. to 160 C. for 5 to 30 minutes.

4. A process of chemically modifying viscose rayon fibers which comprises applying to the fibers an aqueous solution having a pH between 5.0 and 7.5 and containing by weight of the solution 0.25% to about 5.0% ethylene glycol-formaldehyde polymeric acetal, 0.25 to about 5.0% monomeric formaldehyde, 0.05% to 0.5% of the sodium metal salt of an organic acid with at least one carboxylic acid group with an ionization constant lying between 1X10 and 1x10 a nonionic polyoxyethyl ene sorbitol tallow finish, and 0.2% to about 2.0% of magnesium chloride, removing the excess liquid. drying the fibers at between about 70 C. to about 110 C., and finally curing the same by uniformly heating at between 120 C. to 160 C. for 5 to 30 minutes.

References Cited in the file of this patent UNITED STATES PATENTS 2,108,520 Wolf et al Feb. 15, 1938 2,541,457 Beer Feb. 13, 1951 2,585,949 Kress Mar. 19, 1957 2,826,514 Schroeder Mar. 11, 1958 2,945,738 Harmon July 19, 1960 

1. A PROCESS OF CHEMICALLY MODIFYING RAYON FIBERS WHICH COMPRISES APPLYING TO THE FIBERS AN AQUEIOUS SOLUTION HAVING A PH BETWEEN 5.0 AND 7.5 AND CONTAINING BY WEIGHT OF THE SOLUTION 0.25% TO ABOUT 5.0% ETHYLENE GLYCOL-FORMALDEHYDE POLYMERIC ACETAL, 0.25% TO ABUT 5.0% MONOMERIC FORMALDEHYDE, 0.05% TO ABOUT 0.5% OF AN ALKALI METAL SALT OF AN ORGANIC ACID, AND 0.2% TO ABOUT 2.0% OF A CATALYST, REMOVING THE EXCESS LIQUID WHEREBY A PICKUP OF BETWEEN 100% AND 200% IS EFFECTED, DRYING THE FIBER AT BETWEEN ABOUT 70*C. AND 110*C., AND THEREAFTER CURING THE SAME BY UNIFORMLY HEATING AT BETWEEN 120*C. AND 160*C. FOR FROM 5 TO 30 MINUTES. 